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000
FXUS66 KSEW 012143
AFDSEW

Area Forecast Discussion
National Weather Service Seattle WA
243 PM PDT Sat Apr 1 2023

.SYNOPSIS...Upper troughing will be over the Pacific
Northwest through early Tuesday next week for unsettled weather,
including isolated thunderstorms through Sunday. Ridging will
build offshore late Tuesday into Wednesday for a brief period of
drier weather. Another front likely late week around Friday before
ridging builds next weekend.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY/...Showers across Western
Washington this afternoon with embedded thunderstorms observed,
especially near the convergence zone located across northern
portions of Kitsap County and across Snohomish County. The
convergence zone will likely be the focus for continued
thunderstorm potential through the afternoon, however, shower
activity across portions of the coast, Southwest Interior, and
across the southern Puget Sound will also have the potential for
isolated thunderstorms with CAPE values generally 100-400 J/kg.
Small hail and gusty winds will exist within any thunderstorm. In
addition to the thunderstorm potential, periods of snow will
continue for the Olympics and Cascades, including the Passes, with
snow levels generally ranging 1000-2000 feet. As temperatures fall
into the 30s tonight, snow levels will fall to 700-1000 feet, and
there is slight potential for snow to mix in with any heavier
convective shower towards sea level. However, this will be limited
in general, with no impacts expected.

Troughing slides over the Pacific Northwest into Sunday for
continued unsettled weather and the potential for showers and
isolated thunderstorms. The best chance for thunderstorms on
Sunday is expected to be south of Everett (15-25% chance for most
of the area), mainly in the late morning through the afternoon. A
brief area of convergence is likely late afternoon through the
evening across the central Puget Sound which may bring brief
heavier precipitation, including small hail, and an increased
chance for an embedded thunderstorm. Snow for the Cascades will
continue through Sunday evening before tapering off Sunday night
and Monday.

The bulk of the upper trough will slide southeast of the area on
Monday. However, troughing a weak upper low will slide south out
of British Columbia later Monday into Tuesday. This will allow for
another round of light precipitation into Tuesday with cooler air
aloft. Ridging will begin to build offshore later Tuesday for
tapering precipitation chances Tuesday afternoon into Tuesday
night. Temperatures will be below normal through Tuesday with the
upper trough with highs generally ranging upper 40s to low 50s.

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...Ridging will move over
Western Washington into Wednesday, allowing for a brief period of
drier weather. Guidance and ensembles suggest a front will move
towards the area later Thursday into Friday, although there is
some uncertainty on timing. Generally expect precipitation chances
to increase during this period with more west-southwesterly flow,
with temperatures warming a bit further. The majority of guidance
suggests upper ridging to build into the Pacific Northwest on
Saturday, although a weak trough along the northern edge of the
ridge may continue the chance for showers on Saturday, have kept
the NBM forecast for chance of precipitation. Temperatures will
certainly warm through the week, however, with the ridging
influence, with above normal temperatures going into next weekend
with likely highs into the 60s across Western Washington. JD

&&

.AVIATION...Post-frontal flow with a cool upper level trough moving
into Western Washington today. Mix of ceilings with low MVFR to IFR
under showers and near the PSCZ, and generally VFR elsewhere. Expect
continued showers through the day with isolated thunderstorms
possible through around 03z. CZ likely remains north of KBFI/KSEA,
remaining near KPAE/KAWO. Gusty winds, S/SW south of the PSCZ and
NW/W to the north also continue through evening. Finally, showers
overnight may have some snow mixed in, especially 10-15z, which
could lead to lower visibilities. Otherwise, expect to see ceilings
gradually settle into the low VFR to MVFR range most terminals after
12z.

KSEA...Gusty south wind with gusts to 25 kt and occasional
showers (with associated winds and lower ceilings) expected through
the day. An isolated thunderstorm can`t be ruled out this afternoon
and evening. Some showers late tonight/early Sunday (10-15z) may
have some snow mixing in and briefly reduce visibility but don`t
expect accumulation or significant additional impact to the terminal
with rain shadowing lowering overall shower threat.    Cullen

&&

.MARINE...Onshore flow with solid westerlies through the Strait of
Juan de Fuca. Elsewhere, widespread showers across the waters will
provide for gusty winds and the potential for a thunderstorm. Seas
over the coastal waters continue to hold at 8 to 10 ft and remain
rather steep with a mix of west and south components. Expect seas to
hover in this range through the start of the week, and with dominant
periods remaining around 8 to 10 seconds, have extended the small
craft advisory into Sunday morning. Will need to monitor for
potential further extension with seas continuing to run a few feet
above GFS-Wave guidance. High pressure likely builds toward midweek
with relaxing winds and subsiding seas around Wednesday. Cullen

&&

.HYDROLOGY...River flooding not expected for the next 7 days.

&&

.SEW WATCHES/WARNINGS/ADVISORIES...
WA...Winter Weather Advisory until 5 PM PDT this afternoon for
     Olympics.

     Winter Storm Warning until 5 AM PDT Sunday for West Slopes North
     Cascades and Passes.

     Winter Storm Warning until 5 PM PDT Sunday for West Slopes North
     Central Cascades and Passes-West Slopes South Central
     Cascades and Passes.

PZ...Small Craft Advisory until 11 PM PDT this evening for Central
     U.S. Waters Strait Of Juan De Fuca-East Entrance U.S.
     Waters Strait Of Juan De Fuca-Puget Sound and Hood Canal.

     Small Craft Advisory until 11 PM PDT this evening for Northern
     Inland Waters Including The San Juan Islands.

     Small Craft Advisory from 6 PM this evening to midnight PDT
     tonight for Admiralty Inlet.

     Small Craft Advisory until 11 AM PDT Sunday for Coastal Waters
     From Cape Flattery To James Island 10 To 60 Nm-Coastal
     Waters From Cape Flattery To James Island Out 10 Nm-Coastal
     Waters From James Island To Point Grenville 10 To 60 Nm-
     Coastal Waters From James Island To Point Grenville Out 10
     Nm-Coastal Waters From Point Grenville To Cape Shoalwater
     10 To 60 Nm-Coastal Waters From Point Grenville To Cape
     Shoalwater Out 10 Nm.

&&

$$